Why one did not change , a change

  public class A {
  
  	
  	public static void main(String[] args) {
  	
  		String a="af";
  		TE te=new TE();
  		BB bb=new BB();
  		te.test(a);
  		te.test1(bb);
  		System.out.println(a);
  		System.out.println(bb.getB());
  		
  	}
  	
  
  }
  class TE{
  	public String test(String a){
  		a="1";
  		return a;
  	}
  	public String test1(BB bb){
  		String a="1";
  		bb.setB(a);
  		return a;
  	}
  }
  class BB{
  	private String  a;
  	private String b;
  	public String getA() {
  		return a;
  	}
  	public void setA(String a) {
  		this.a = a;
  	}
  	public String getB() {
  		return b;
  	}
  	public void setB(String b) {
  		this.b = b;
  	}
  	
  }
  
  
  

------ Solution ------------------------------------- -------
java is passed by value.
http://bbs.csdn.net/topics/90058535
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a = te.test (a);
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upstairs was right , test methods have not changed so you do not have to receive , test1 change is referenced inside the property so changed


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1 floor right
two different memory addresses pointing
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a output must be af, as a reference point has not changed , upstairs solution
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you directly
System.out.println (a);
System.out.println (te.test (a));
to know why
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you just performed for a TE in the test (String a) method, but did not put value back to a, the output is directly in front of the definition of a