Java中参数的传递方法

Java语言中参数传递是常见的问题之一，通过阅读如下测试代码，可以看看你是否真的了解java常见的参数传递的规则。

Java代码：

public class TestChangeParamInt {

    public static void main(String[] args) {
        int n = 3;
        System.out.println("Before change : " + n);
        
        changeData(n);
        System.out.println("After changeData(n) : " + n);
    }

    public static void changeData(int n) {
        n = 10;
    }

}

public class TestChangeParamObj1 {    

    public static void changeData(StringBuffer strBuffer) {
        strBuffer.append("World!");
    }

    public static void main(String[] args) {
        StringBuffer strBuffer = new StringBuffer("Hello ");
        System.out.println("Before change : " + strBuffer);

        changeData(strBuffer);
        System.out.println("After changeData(n) : " + strBuffer);
    }
}


public class TestChangeParamObj2 {

    public static void main(String[] args) {
        StringBuffer strBuffer = new StringBuffer("main ");
        System.out.println("Before change = " + strBuffer);
        
        changeData(strBuffer);
        System.out.println("After changeData(n) = " + strBuffer);
    }

    public static void changeData(StringBuffer strBuffer) {
        strBuffer = new StringBuffer("Change ");
        strBuffer.append("World!");
    }

}

public class TestChangeParamObj3 {

    public static void main(String[] args) {
        StringBuffer strBuffer = new StringBuffer("Hello ");
        System.out.println("Before change = " + strBuffer);

        changeData(strBuffer);
        System.out.println("After changeData(n) = " + strBuffer);
    }
    
    public static void changeData(StringBuffer strBuffer) {
        StringBuffer sb2 = new StringBuffer("change ");
        strBuffer = sb2;
        sb2.append("World!");
        System.out.println("In changeData(n) = " + sb2);
    }

}