java参数传递

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。

 

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);
	}

}