Java中的按值传递和按引用传递的代码详解

public class TTEST { 
  private static  List<UserEntity> mList = new LinkedList<UserEntity>();  
  public static void main(String[] args) { 
    int a = 0; 
    changeA(a); 
    System.out.println("a = "+a); 
  } 
   
  public static void changeA(int a){ 
    a = 1; 
  } 
}

public class UserEntity { 
  private String name; 
  public String getName() { 
    return name; 
  } 
  public void setName(String name) { 
    this.name = name; 
  } 
} 

public class TTEST { 
  public static void main(String[] args) { 
    UserEntity userEntity = new UserEntity(); 
    userEntity.setName("猿猴"); 
    changeName(userEntity); 
    System.out.println("name = "+userEntity.getName()); 
  } 
  public static void changeName(UserEntity userEntity){ 
    userEntity.setName("忽必烈"); 
  } 
} 

import java.util.LinkedList; 
import java.util.List; 
public class TTEST { 
   private static List<UserEntity> mList = new LinkedList<UserEntity>();  
  public static void main(String[] args) { 
    UserEntity userEntity = new UserEntity(); 
    userEntity.setName("石头"); 
    addUser(userEntity); 
    System.out.println("name = "+userEntity.getName()); 
  } 
  public static void addUser(UserEntity userEntity){ 
    mList.add(userEntity); 
    mList.get(0).setName("猿猴"); 
  } 
} 

public class TTEST { 
  public static void main(String[] args) { 
    String str= "开始的"; 
    changeStr(str); 
    System.out.println("str = "+str); 
  } 
  public static void changeStr(String str){ 
    str = "改变的"; 
  } 
}