diff --git a/gradle-modules/gradle-5/cmd-line-args/build.gradle b/gradle-modules/gradle-5/cmd-line-args/build.gradle
index 15c9288024..a40b04a7a1 100644
--- a/gradle-modules/gradle-5/cmd-line-args/build.gradle
+++ b/gradle-modules/gradle-5/cmd-line-args/build.gradle
@@ -7,6 +7,8 @@ ext.javaMainClass = "com.baeldung.cmd.MainClass"
 application {
     mainClassName = javaMainClass
 }
+sourceCompatibility = "1.8"
+targetCompatibility = "1.8"
 
 task propertyTypes(){
     doLast{
diff --git a/gradle-modules/gradle-5/gradle-lint-intro/build.gradle b/gradle-modules/gradle-5/gradle-lint-intro/build.gradle
index fab83bfeec..ba32d53605 100644
--- a/gradle-modules/gradle-5/gradle-lint-intro/build.gradle
+++ b/gradle-modules/gradle-5/gradle-lint-intro/build.gradle
@@ -5,6 +5,9 @@ ext {
     awsVersion = '2.20.83'
 }
 
+sourceCompatibility = "1.8"
+targetCompatibility = "1.8"
+
 
 dependencies {
     implementation platform("software.amazon.awssdk:bom:$awsVersion")
diff --git a/gradle-modules/gradle-5/java-exec/build.gradle b/gradle-modules/gradle-5/java-exec/build.gradle
index 08aa738902..67ea3e3d39 100644
--- a/gradle-modules/gradle-5/java-exec/build.gradle
+++ b/gradle-modules/gradle-5/java-exec/build.gradle
@@ -13,6 +13,8 @@ jar {
         )
     }
 }
+sourceCompatibility = "1.8"
+targetCompatibility = "1.8"
 
 application {
     mainClassName = javaMainClass
diff --git a/gradle-modules/gradle-5/source-sets/build.gradle b/gradle-modules/gradle-5/source-sets/build.gradle
index 8325450cfd..8a65e5a845 100644
--- a/gradle-modules/gradle-5/source-sets/build.gradle
+++ b/gradle-modules/gradle-5/source-sets/build.gradle
@@ -3,6 +3,9 @@ apply plugin: "eclipse"
 apply plugin: "java"
 
 description = "Source Sets example"
+sourceCompatibility = "1.8"
+targetCompatibility = "1.8"
+
 
 task printSourceSetInformation(){
     description = "Print source set information"
diff --git a/gradle-modules/gradle-5/unused-dependencies/build.gradle b/gradle-modules/gradle-5/unused-dependencies/build.gradle
index d848cd0e0d..028224519c 100644
--- a/gradle-modules/gradle-5/unused-dependencies/build.gradle
+++ b/gradle-modules/gradle-5/unused-dependencies/build.gradle
@@ -1,6 +1,9 @@
 
 description = "Gradle Unused Dependencies example"
 
+sourceCompatibility = "1.8"
+targetCompatibility = "1.8"
+
 dependencies {
     implementation('com.google.guava:guava:29.0-jre')
     implementation('org.apache.httpcomponents:httpclient:4.5.12')
diff --git a/gradle-modules/gradle-6/dependency-constraints/build.gradle.kts b/gradle-modules/gradle-6/dependency-constraints/build.gradle.kts
index 41336d3c91..138dbcc595 100644
--- a/gradle-modules/gradle-6/dependency-constraints/build.gradle.kts
+++ b/gradle-modules/gradle-6/dependency-constraints/build.gradle.kts
@@ -4,6 +4,8 @@ plugins {
 
 group = "com.baeldung"
 version = "1.0.0"
+sourceCompatibility = "1.8"
+targetCompatibility = "1.8"
 
 dependencies {
     api("io.reactivex.rxjava2:rxjava:2.2.16")
diff --git a/gradle-modules/gradle-6/fibonacci-recursive/build.gradle.kts b/gradle-modules/gradle-6/fibonacci-recursive/build.gradle.kts
index 0872a52472..884175577f 100644
--- a/gradle-modules/gradle-6/fibonacci-recursive/build.gradle.kts
+++ b/gradle-modules/gradle-6/fibonacci-recursive/build.gradle.kts
@@ -2,6 +2,9 @@ plugins {
     `java-library`
 }
 
+sourceCompatibility = "1.8"
+targetCompatibility = "1.8"
+
 dependencies {
     api(project(":fibonacci-spi"))
     compileOnly("com.google.auto.service:auto-service-annotations:1.0-rc6")
diff --git a/gradle-modules/gradle-6/fibonacci-spi/build.gradle.kts b/gradle-modules/gradle-6/fibonacci-spi/build.gradle.kts
index e571f329a9..b468793a3f 100644
--- a/gradle-modules/gradle-6/fibonacci-spi/build.gradle.kts
+++ b/gradle-modules/gradle-6/fibonacci-spi/build.gradle.kts
@@ -3,6 +3,9 @@ plugins {
     `java-test-fixtures`
 }
 
+sourceCompatibility = "1.8"
+targetCompatibility = "1.8"
+
 dependencies {
     testFixturesApi("org.junit.jupiter:junit-jupiter-api:5.5.2")
     testFixturesImplementation("org.junit.jupiter:junit-jupiter-engine:5.5.2")
diff --git a/gradle-modules/gradle-6/httpclient-platform/build.gradle.kts b/gradle-modules/gradle-6/httpclient-platform/build.gradle.kts
index a021bff013..693f4e5452 100644
--- a/gradle-modules/gradle-6/httpclient-platform/build.gradle.kts
+++ b/gradle-modules/gradle-6/httpclient-platform/build.gradle.kts
@@ -2,6 +2,9 @@ plugins {
     `java-platform`
 }
 
+sourceCompatibility = "1.8"
+targetCompatibility = "1.8"
+
 dependencies {
     constraints {
         api("org.apache.httpcomponents:fluent-hc:4.5.10")
diff --git a/gradle-modules/gradle-6/module-metadata-publishing/build.gradle.kts b/gradle-modules/gradle-6/module-metadata-publishing/build.gradle.kts
index 9812c72f6f..382f989e7c 100644
--- a/gradle-modules/gradle-6/module-metadata-publishing/build.gradle.kts
+++ b/gradle-modules/gradle-6/module-metadata-publishing/build.gradle.kts
@@ -3,6 +3,9 @@ plugins {
     `maven-publish`
 }
 
+sourceCompatibility = "1.8"
+targetCompatibility = "1.8"
+
 publishing {
     publications {
         register<MavenPublication>("mavenJava") {
diff --git a/gradle-modules/gradle-6/person-rest-client/build.gradle.kts b/gradle-modules/gradle-6/person-rest-client/build.gradle.kts
index c562b3e164..3ca9d21adc 100644
--- a/gradle-modules/gradle-6/person-rest-client/build.gradle.kts
+++ b/gradle-modules/gradle-6/person-rest-client/build.gradle.kts
@@ -2,6 +2,9 @@ plugins {
     `java-library`
 }
 
+sourceCompatibility = "1.8"
+targetCompatibility = "1.8"
+
 dependencies {
     api(platform(project(":httpclient-platform")))
     implementation("org.apache.httpcomponents:fluent-hc")
diff --git a/gradle-modules/gradle-6/widget-rest-client/build.gradle.kts b/gradle-modules/gradle-6/widget-rest-client/build.gradle.kts
index e1af4b7f71..2f5842b8dc 100644
--- a/gradle-modules/gradle-6/widget-rest-client/build.gradle.kts
+++ b/gradle-modules/gradle-6/widget-rest-client/build.gradle.kts
@@ -2,6 +2,9 @@ plugins {
     `java-library`
 }
 
+sourceCompatibility = "1.8"
+targetCompatibility = "1.8"
+
 dependencies {
     api(platform(project(":httpclient-platform")))
     implementation("org.apache.httpcomponents:httpclient")
diff --git a/gradle-modules/gradle-7/conditional-dependency-demo/build.gradle.kts b/gradle-modules/gradle-7/conditional-dependency-demo/build.gradle.kts
index 95601a160d..935a23d56f 100644
--- a/gradle-modules/gradle-7/conditional-dependency-demo/build.gradle.kts
+++ b/gradle-modules/gradle-7/conditional-dependency-demo/build.gradle.kts
@@ -6,6 +6,8 @@ plugins {
 
 group = "com.baeldung.gradle"
 version = "0.0.1-SNAPSHOT"
+sourceCompatibility = "1.8"
+targetCompatibility = "1.8"
 
 repositories {
 	mavenCentral()
diff --git a/gradle-modules/gradle-7/conditional-dependency-demo/consumer1/build.gradle.kts b/gradle-modules/gradle-7/conditional-dependency-demo/consumer1/build.gradle.kts
index 9858c5b139..5f266cae7a 100644
--- a/gradle-modules/gradle-7/conditional-dependency-demo/consumer1/build.gradle.kts
+++ b/gradle-modules/gradle-7/conditional-dependency-demo/consumer1/build.gradle.kts
@@ -4,6 +4,8 @@ plugins {
 
 group = "com.baeldung.gradle"
 version = "0.0.1-SNAPSHOT"
+sourceCompatibility = "1.8"
+targetCompatibility = "1.8"
 
 repositories {
     mavenCentral()
diff --git a/gradle-modules/gradle-7/conditional-dependency-demo/consumer2/build.gradle.kts b/gradle-modules/gradle-7/conditional-dependency-demo/consumer2/build.gradle.kts
index 2031aea59c..70a16e2971 100644
--- a/gradle-modules/gradle-7/conditional-dependency-demo/consumer2/build.gradle.kts
+++ b/gradle-modules/gradle-7/conditional-dependency-demo/consumer2/build.gradle.kts
@@ -4,6 +4,8 @@ plugins {
 
 group = "com.baeldung.gradle"
 version = "0.0.1-SNAPSHOT"
+sourceCompatibility = "1.8"
+targetCompatibility = "1.8"
 
 repositories {
     mavenCentral()
diff --git a/gradle-modules/gradle-7/conditional-dependency-demo/provider1/build.gradle.kts b/gradle-modules/gradle-7/conditional-dependency-demo/provider1/build.gradle.kts
index d3dcd96b08..8601796ac4 100644
--- a/gradle-modules/gradle-7/conditional-dependency-demo/provider1/build.gradle.kts
+++ b/gradle-modules/gradle-7/conditional-dependency-demo/provider1/build.gradle.kts
@@ -4,6 +4,8 @@ plugins {
 
 group = "com.baeldung.gradle"
 version = "0.0.1-SNAPSHOT"
+sourceCompatibility = "1.8"
+targetCompatibility = "1.8"
 
 repositories {
     mavenCentral()
diff --git a/gradle-modules/gradle-7/conditional-dependency-demo/provider2/build.gradle.kts b/gradle-modules/gradle-7/conditional-dependency-demo/provider2/build.gradle.kts
index d3dcd96b08..8601796ac4 100644
--- a/gradle-modules/gradle-7/conditional-dependency-demo/provider2/build.gradle.kts
+++ b/gradle-modules/gradle-7/conditional-dependency-demo/provider2/build.gradle.kts
@@ -4,6 +4,8 @@ plugins {
 
 group = "com.baeldung.gradle"
 version = "0.0.1-SNAPSHOT"
+sourceCompatibility = "1.8"
+targetCompatibility = "1.8"
 
 repositories {
     mavenCentral()
diff --git a/gradle-modules/gradle-7/gradle-javadoc/build.gradle b/gradle-modules/gradle-7/gradle-javadoc/build.gradle
index 5d8303d64c..761d911ad8 100644
--- a/gradle-modules/gradle-7/gradle-javadoc/build.gradle
+++ b/gradle-modules/gradle-7/gradle-javadoc/build.gradle
@@ -4,6 +4,8 @@ plugins {
 
 group 'org.example'
 version '1.0-SNAPSHOT'
+sourceCompatibility = "1.8"
+targetCompatibility = "1.8"
 
 javadoc {
     destinationDir = file("${buildDir}/docs/javadoc")
diff --git a/gradle-modules/gradle-7/gradle-proxy-configuration/build.gradle b/gradle-modules/gradle-7/gradle-proxy-configuration/build.gradle
index 7463486961..c6e10b053e 100644
--- a/gradle-modules/gradle-7/gradle-proxy-configuration/build.gradle
+++ b/gradle-modules/gradle-7/gradle-proxy-configuration/build.gradle
@@ -4,6 +4,8 @@ plugins {
 
 group = 'org.baeldung'
 version = '1.0-SNAPSHOT'
+sourceCompatibility = "1.8"
+targetCompatibility = "1.8"
 
 repositories {
     mavenCentral()
diff --git a/gradle-modules/gradle-7/gradle-wsdl-stubs/build.gradle b/gradle-modules/gradle-7/gradle-wsdl-stubs/build.gradle
index 6d0cfc1972..3917c2f401 100644
--- a/gradle-modules/gradle-7/gradle-wsdl-stubs/build.gradle
+++ b/gradle-modules/gradle-7/gradle-wsdl-stubs/build.gradle
@@ -3,6 +3,9 @@ plugins {
     id 'com.github.bjornvester.wsdl2java' version '2.0.2'
 }
 
+sourceCompatibility = "1.8"
+targetCompatibility = "1.8"
+
 repositories {
     mavenCentral()
 }
diff --git a/gradle-modules/gradle-7/multiple-repositories-demo/publish-package/build.gradle b/gradle-modules/gradle-7/multiple-repositories-demo/publish-package/build.gradle
index bd97650e9c..89d77ddcae 100644
--- a/gradle-modules/gradle-7/multiple-repositories-demo/publish-package/build.gradle
+++ b/gradle-modules/gradle-7/multiple-repositories-demo/publish-package/build.gradle
@@ -5,6 +5,8 @@ plugins {
 
 group = "com.baeldung.gradle"
 version = "1.0.0-SNAPSHOT"
+sourceCompatibility = "1.8"
+targetCompatibility = "1.8"
 
 repositories {
     mavenLocal()
diff --git a/gradle-modules/gradle/gradle-employee-app/build.gradle b/gradle-modules/gradle/gradle-employee-app/build.gradle
index c7040504f1..03d28f7e20 100644
--- a/gradle-modules/gradle/gradle-employee-app/build.gradle
+++ b/gradle-modules/gradle/gradle-employee-app/build.gradle
@@ -6,8 +6,8 @@ plugins {
 apply plugin: 'application'
 mainClassName = 'employee.EmployeeApp'
 
-sourceCompatibility = JavaVersion.VERSION_1_8
-targetCompatibility = JavaVersion.VERSION_1_8
+sourceCompatibility = "1.8"
+targetCompatibility = "1.8"
 
 println 'This is executed during configuration phase'
 
diff --git a/gradle-modules/gradle/gradle-fat-jar/build.gradle b/gradle-modules/gradle/gradle-fat-jar/build.gradle
index 4c3d86d757..55fbf2d748 100644
--- a/gradle-modules/gradle/gradle-fat-jar/build.gradle
+++ b/gradle-modules/gradle/gradle-fat-jar/build.gradle
@@ -13,6 +13,9 @@ plugins {
   id 'java'
 }
 
+sourceCompatibility = JavaVersion.VERSION_1_8
+targetCompatibility = JavaVersion.VERSION_1_8
+
 repositories {
     mavenCentral()
 }
diff --git a/gradle-modules/gradle/gradle-to-maven/build.gradle b/gradle-modules/gradle/gradle-to-maven/build.gradle
index 7cd2617ef4..87f4272c13 100644
--- a/gradle-modules/gradle/gradle-to-maven/build.gradle
+++ b/gradle-modules/gradle/gradle-to-maven/build.gradle
@@ -10,6 +10,8 @@ group = 'com.baeldung'
 // by default, pom's artifactId is taken from the directory name
 
 version = '0.0.1'
+sourceCompatibility = JavaVersion.VERSION_1_8
+targetCompatibility = JavaVersion.VERSION_1_8
 
 dependencies {
     implementation 'org.slf4j:slf4j-api:1.7.25'
diff --git a/gradle-modules/gradle/gradletaskdemo/build.gradle b/gradle-modules/gradle/gradletaskdemo/build.gradle
index 5f07573365..cb8f285fa0 100644
--- a/gradle-modules/gradle/gradletaskdemo/build.gradle
+++ b/gradle-modules/gradle/gradletaskdemo/build.gradle
@@ -13,6 +13,9 @@ plugins {
     id 'java'
 }
 
+sourceCompatibility = JavaVersion.VERSION_1_8
+targetCompatibility = JavaVersion.VERSION_1_8
+
 apply from: 'aplugin.gradle'
 apply plugin: 'org.shipkit.bintray-release'
 
diff --git a/gradle-modules/gradle/greeter/build.gradle b/gradle-modules/gradle/greeter/build.gradle
index 0aab8c2313..bc6f800ea0 100644
--- a/gradle-modules/gradle/greeter/build.gradle
+++ b/gradle-modules/gradle/greeter/build.gradle
@@ -1,6 +1,9 @@
 apply plugin : 'java'
 apply plugin : 'application'
 
+sourceCompatibility = JavaVersion.VERSION_1_8
+targetCompatibility = JavaVersion.VERSION_1_8
+
 dependencies {
     implementation project(':greeting-library')
     implementation project(':greeting-library-java')
diff --git a/gradle-modules/gradle/greeting-library-java/build.gradle b/gradle-modules/gradle/greeting-library-java/build.gradle
index 916a9a435e..778536ba49 100644
--- a/gradle-modules/gradle/greeting-library-java/build.gradle
+++ b/gradle-modules/gradle/greeting-library-java/build.gradle
@@ -1,6 +1,9 @@
 apply plugin :'java'
 //apply plugin : 'application'
 
+sourceCompatibility = JavaVersion.VERSION_1_8
+targetCompatibility = JavaVersion.VERSION_1_8
+
 dependencies{
     implementation group: 'joda-time', name: 'joda-time', version: '2.9.9'
     testImplementation group: 'junit', name: 'junit', version: '4.12'
diff --git a/gradle-modules/gradle/greeting-library/build.gradle b/gradle-modules/gradle/greeting-library/build.gradle
index a8fa91963c..16304cd5ed 100644
--- a/gradle-modules/gradle/greeting-library/build.gradle
+++ b/gradle-modules/gradle/greeting-library/build.gradle
@@ -7,3 +7,8 @@ dependencies {
         exclude module : 'groovy-all'
     }
 }
+
+java {
+    sourceCompatibility = JavaVersion.VERSION_1_8
+    targetCompatibility = JavaVersion.VERSION_1_8
+}
diff --git a/gradle-modules/gradle/junit5/build.gradle b/gradle-modules/gradle/junit5/build.gradle
index e589541e08..41c870e6f6 100644
--- a/gradle-modules/gradle/junit5/build.gradle
+++ b/gradle-modules/gradle/junit5/build.gradle
@@ -3,6 +3,9 @@ plugins {
     id 'java-library'
 }
 
+sourceCompatibility = JavaVersion.VERSION_1_8
+targetCompatibility = JavaVersion.VERSION_1_8
+
 dependencies {
     testImplementation 'org.junit.jupiter:junit-jupiter-api:5.3.1'
     testRuntimeOnly 'org.junit.jupiter:junit-jupiter-engine:5.3.1'