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Testing Java Reference Behavior and Parameter Passing in JCSprout

This test suite explores Java reference behavior and parameter passing mechanisms through comprehensive unit tests. It validates both primitive and object reference handling, demonstrating key differences in how Java manages memory and object references.

Test Coverage Overview

The test suite provides thorough coverage of Java reference mechanics and parameter passing.

Key areas tested include:

Primitive type parameter passing
Object reference modification
List reference handling
Object reassignment scenarios
Collection modification through references

Implementation Analysis

The testing approach employs JUnit to verify Java’s pass-by-value behavior for both primitives and references. Tests demonstrate how modifications affect original variables and objects, using a custom Car class and ArrayList implementations to showcase different reference scenarios.

Technical patterns include:

Before/after state verification
Object modification tracking
Collection manipulation testing

Technical Details

Testing infrastructure includes:

JUnit 4 framework
Java 11 runtime
Custom Car class for object reference testing
ArrayList for collection reference testing
System.out.println for state tracking

Best Practices Demonstrated

The test suite exemplifies strong testing practices through clear test case isolation and comprehensive scenario coverage.

Notable practices include:

Isolated test methods for specific scenarios
Clear test naming conventions
Comprehensive primitive vs reference type testing
Systematic state verification

crossoverjie/jcsprout

src/test/java/com/crossoverjie/reference/ReferenceTest.java

            
package com.crossoverjie.reference;

import org.junit.Test;

import java.util.ArrayList;
import java.util.List;

/**
 * Function:
 *
 * @author crossoverJie
 * Date: 2020/12/19 00:18
 * @since JDK 11
 */
public class ReferenceTest {

    @Test
    public void testBasic() {
        int a = 10;
        modifyBasic(a);
        System.out.println(String.format("最终结果 main a==%s", a));
    }


    private void modifyBasic(int aa) {
        System.out.println(String.format("修改之前 aa==%s", aa));
        aa = 20;
        System.out.println(String.format("修改之后 aa==%s", aa));
    }

    @Test
    public void testReference01(){
        Car car1 = new Car("benz");
        modifyCar1(car1);
        System.out.println(String.format("最终结果 main car1==%s", car1));
    }

    private void modifyCar1(Car car){
        System.out.println(String.format("修改之前 car==%s", car));
        car.name = "bwm";
        System.out.println(String.format("修改之后 car==%s", car));
    }

    @Test
    public void testList(){
        List<Integer> list = new ArrayList<>();
        list.add(1);
        addList(list);
        System.out.println(list);
    }

    private void addList(List<Integer> list) {
        list.add(2);
    }

    @Test
    public void test02(){
        Car car1 = new Car("benz");
        modifyCar(car1);
        System.out.println(String.format("最终结果 main car1==%s", car1));
    }

    private void modifyCar(Car car2) {
        System.out.println(String.format("修改之前 car2==%s", car2));
        car2 = new Car("bmw");
        System.out.println(String.format("修改之后 car2==%s", car2));
    }

    private class Car{
        private String name;

        public Car(String name) {
            this.name = name;
        }

        @Override
        public String toString() {
            return "Car{" +
                    "name='" + name + '\'' +
                    '}';
        }
    }

    @Test
    public void testReference03() {
        List<Integer> a = new ArrayList<>();
        a.add(1);
        modifyReference02(a);
        System.out.println(String.format("Final main a==%s", a));

    }

    private void modifyReference02(List<Integer> aa) {
        System.out.println(String.format("Before modify aa==%s", aa));
        aa.add(2);
        System.out.println(String.format("After modify aa==%s", aa));
    }
}