java 方法传值浅拷贝验证

source code

import org.junit.Test;

public class SigmoidTruncatedSuit {
    @Test
    public void main_test() {
        Float xs = 3f;
        System.out.println(String.format("Float origin : %s",xs));
        convert(xs);
        System.out.println(String.format("Float convert : %s",xs));
        java.util.HashMap<Integer, Float> m = new java.util.HashMap<>();
        m.put(0,1f);
        System.out.println(String.format("HashMap origin : %s",m.get(0)));
        cct(m);
        System.out.println(String.format("HashMap convert : %s",m.get(0)));
    }
    public void convert(Float x) {
        System.out.println(String.format("Float inner origin : %s",x));
        x = 13f;
        System.out.println(String.format("Float inner convert : %s",x));
    }
    public void cct(java.util.HashMap<Integer, Float> m){
        System.out.println(String.format("HashMap inner origin : %s",m.get(0)));
        m.put(0,13f);
        m = new java.util.HashMap<>();
        System.out.println(String.format("HashMap inner convert : %s",m.get(0)));
    }

output

Float origin : 3.0
Float inner origin : 3.0
Float inner convert : 13.0
Float convert : 3.0
HashMap origin : 1.0
HashMap inner origin : 1.0
HashMap inner convert : null
HashMap convert : 13.0

结论

• Java方法参数传递为值传递
• Java方法值传递为浅拷贝
• Scala 类似