Home/ Questions/The solution for ''error: java.lang.verifyerror: bad type on operand stack'' ?
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thereseblanda
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Asked: 2022-08-06T04:32:49+00:00 In:

The solution for ”error: java.lang.verifyerror: bad type on operand stack” ?

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Today I still get the ”error: java.lang.verifyerror: bad type on operand stack”  error when running my program.

public class TestJavaCodes {

int parentData = 0;

public void init() {
A ob = new B();
}

public static void main(String[] args) {

TestJavaCodes testJavaCodes = new TestJavaCodes();
testJavaCodes.init();
}

public static class A {
public A(MyLambdaFunc lambdaFunc) {
}
}

public class B extends A {

public B() {
super((data1, type) -> {
parentData = 1;
});
}
}

@FunctionalInterface
public static interface MyLambdaFunc {
public void onData(String data, int type);
}
}

I don’t know what the reason is and the way to fix it? Can you help me?

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1 Answer

  1. Best Answer
    Expert

    The cause: The issue arises because your lambda expression refers to a member of the outer this rather than this or a member of this. Had you written class B like

    public class B extends A {
int innerData;
public B() {
super((data1, type) -> innerData = 1);
}
}

    the compiler rejected it since accessing innerData implies accessing this.

    Solution: The lambda expression refers to the outer instance without accessing the inner instance with the small change below, and no error occurs.

    public class B extends A {
public B() {
this(TestJavaCodes.this);
}
private B(TestJavaCodes outer) {
super((data1, type) -> outer.parentData = 1);
}
}
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