From c65981938f9be61a5182259c911462a21671a940 Mon Sep 17 00:00:00 2001
From: lucaCambi77 <lucacambi77@gmail.com>
Date: Sat, 28 Oct 2023 23:56:11 +0200
Subject: [PATCH] [BAEL-7048] - Passing Strings By Reference in Java (#15047)

* feat: pass by reference java string

* fix: review
---
 .../baeldung/passstringbyreference/Dummy.java | 14 +++
 .../PassStringUnitTest.java                   | 85 +++++++++++++++++++
 2 files changed, 99 insertions(+)
 create mode 100644 core-java-modules/core-java-strings/src/test/java/com/baeldung/passstringbyreference/Dummy.java
 create mode 100644 core-java-modules/core-java-strings/src/test/java/com/baeldung/passstringbyreference/PassStringUnitTest.java

diff --git a/core-java-modules/core-java-strings/src/test/java/com/baeldung/passstringbyreference/Dummy.java b/core-java-modules/core-java-strings/src/test/java/com/baeldung/passstringbyreference/Dummy.java
new file mode 100644
index 0000000000..27ebf8331f
--- /dev/null
+++ b/core-java-modules/core-java-strings/src/test/java/com/baeldung/passstringbyreference/Dummy.java
@@ -0,0 +1,14 @@
+package com.baeldung.passstringbyreference;
+
+public class Dummy {
+
+    String dummyString;
+
+    public String getDummyString() {
+        return dummyString;
+    }
+
+    public void setDummyString(String dummyString) {
+        this.dummyString = dummyString;
+    }
+}
diff --git a/core-java-modules/core-java-strings/src/test/java/com/baeldung/passstringbyreference/PassStringUnitTest.java b/core-java-modules/core-java-strings/src/test/java/com/baeldung/passstringbyreference/PassStringUnitTest.java
new file mode 100644
index 0000000000..e1b284a94e
--- /dev/null
+++ b/core-java-modules/core-java-strings/src/test/java/com/baeldung/passstringbyreference/PassStringUnitTest.java
@@ -0,0 +1,85 @@
+package com.baeldung.passstringbyreference;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNull;
+
+import org.junit.jupiter.api.Test;
+
+class PassStringUnitTest {
+
+    @Test
+    void givenAString_whenPassedToVoidMethod_thenStringIsNotModified() {
+        String s = "hello";
+        concatStringWithNoReturn(s);
+        assertEquals("hello", s);
+    }
+
+    void concatStringWithNoReturn(String input) {
+        input += " world";
+        assertEquals("hello world", input);
+    }
+
+    @Test
+    void givenAString_whenPassedToMethodAndReturnNewString_thenStringIsModified() {
+        String s = "hello";
+        assertEquals("hello world", concatStringWithReturn(s));
+    }
+
+    String concatStringWithReturn(String input) {
+        return input + " world";
+    }
+
+    @Test
+    void givenAString_whenPassStringBuilderToVoidMethod_thenConcatNewStringOk() {
+        StringBuilder builder = new StringBuilder("hello");
+        concatWithStringBuilder(builder);
+
+        assertEquals("hello world", builder.toString());
+    }
+
+    void concatWithStringBuilder(StringBuilder input) {
+        input.append(" world");
+    }
+
+    @Test
+    void givenAString_whenPassStringBufferToVoidMethod_thenConcatNewStringOk() {
+        StringBuffer builder = new StringBuffer("hello");
+        concatWithStringBuffer(builder);
+
+        assertEquals("hello world", builder.toString());
+    }
+
+    void concatWithStringBuffer(StringBuffer input) {
+        input.append(" world");
+    }
+
+    @Test
+    void givenObjectWithStringField_whenSetDifferentValue_thenObjectIsModified() {
+        Dummy dummy = new Dummy();
+        assertNull(dummy.getDummyString());
+        modifyStringValueInInputObject(dummy, "hello world");
+        assertEquals("hello world", dummy.getDummyString());
+    }
+
+    void modifyStringValueInInputObject(Dummy dummy, String dummyString) {
+        dummy.setDummyString(dummyString);
+    }
+
+    @Test
+    void givenObjectWithStringField_whenSetDifferentValueWithStringBuilder_thenSetStringInNewObject() {
+        assertEquals("hello world", getDummy("hello", "world").getDummyString());
+    }
+
+    Dummy getDummy(String hello, String world) {
+        StringBuilder builder = new StringBuilder();
+
+        builder.append(hello)
+          .append(" ")
+          .append(world);
+
+        Dummy dummy = new Dummy();
+        dummy.setDummyString(builder.toString());
+
+        return dummy;
+    }
+}