113 lines
2.8 KiB
Java
113 lines
2.8 KiB
Java
package com.baeldung.annotations;
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import java.util.List;
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import org.apache.commons.lang3.StringUtils;
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import org.jetbrains.annotations.Contract;
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public class Demo {
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@Contract("_ -> new")
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Person fromName(String name) {
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return new Person().withName(name);
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}
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@Contract(" -> fail")
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void alwaysFail() {
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throw new RuntimeException();
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}
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@Contract(" -> fail")
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void doNothingWithWrongContract() {
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}
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@Contract("_, null -> null; null, _ -> param2; _, !null -> !null")
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String concatenateOnlyIfSecondArgumentIsNotNull(String head, String tail) {
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if (tail == null) {
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return null;
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}
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if (head == null) {
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return tail;
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}
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return head + tail;
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}
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void uselessNullCheck() {
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String head = "1234";
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String tail = "5678";
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String concatenation = concatenateOnlyIfSecondArgumentIsNotNull(head, tail);
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if (concatenation != null) {
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System.out.println(concatenation);
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}
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}
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void uselessNullCheckOnInferredAnnotation() {
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if (StringUtils.isEmpty(null)) {
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System.out.println("baeldung");
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}
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}
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@Contract(pure = true)
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String replace(String string, char oldChar, char newChar) {
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return string.replace(oldChar, newChar);
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}
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@Contract(value = "true -> false; false -> true", pure = true)
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boolean not(boolean input) {
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return !input;
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}
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@Contract("true -> new")
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void contractExpectsWrongParameterType(List<Integer> integers) {
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}
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@Contract("_, _ -> new")
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void contractExpectsMoreParametersThanMethodHas(String s) {
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}
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@Contract("_ -> _; null -> !null")
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String secondContractClauseNotReachable(String s) {
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return "";
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}
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@Contract("_ -> true")
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void contractExpectsWrongReturnType(String s) {
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}
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// NB: the following examples demonstrate how to use the mutates attribute of the annotation
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// This attribute is currently experimental and could be changed or removed in the future
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@Contract(mutates = "param")
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void incrementArrayFirstElement(Integer[] integers) {
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if (integers.length > 0) {
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integers[0] = integers[0] + 1;
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}
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}
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@Contract(pure = true, mutates = "param")
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void impossibleToMutateParamInPureFunction(List<String> strings) {
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if (strings != null) {
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strings.forEach(System.out::println);
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}
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}
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@Contract(mutates = "param3")
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void impossibleToMutateThirdParamWhenMethodHasOnlyTwoParams(int a, int b) {
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}
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@Contract(mutates = "param")
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void impossibleToMutableImmutableType(String s) {
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}
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@Contract(mutates = "this")
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static void impossibleToMutateThisInStaticMethod() {
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}
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}
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